1. Field of the Invention
This invention relates to a particulate fluorescent material formed of a mixture of yttrium oxide and europium oxide and to a process of preparing same.
2. Description of the Related Art
A mixture of yttrium oxide and europium oxide is utilized as a fluorescent material such as for a fluorescent paint. One known method for the production of such a fluorescent material includes the steps of blending a yttrium compound with a europium compound, calcining the blend to form a mixture of yttrium oxide and europium oxide, fusing the mixture to obtain a homogeneous admixture, and grinding the admixture, after cooling, into particles. The fluorescent material of the thus obtained particles has a problem because the particles are not uniform in size and are not spherical in shape. Thus, a paint using such a fluorescent material fails to give a smooth coating.
Sordelet et al propose a method for the preparation of spherical, monosized yttrium oxide particles in which an aqueous yttrium nitrate solution containing urea is heated to precipitate YOHCO.sub.3 particles, the resulting YOHCO.sub.3 particles being subsequently calcined to obtain the spherical yttrium oxide particles (Journal of Colloid and Interface Science, vol. 122, No. 1, pages 47-59, March (1988)).
A process is also known in which an aqueous europium compound solution containing urea is heated to precipitate EuOHCO.sub.3 particles which are convertible to europium oxide particles by calcination.